This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. CmlS is a flavin-dependent halogenase believed to take part in the biosynthesis of chloramphenical. CmlS is thought to dichlorinate the acetyl moiety of the antibiotic although nothing to date is known about it's mechanism of operation or substrate specificity. CmlS is novel in that it is one of few flavin-dependent halogenases believed to act upon a aliphatic rather than aromatic substrate. By crystallizing CmlS there is hope to gain information as to its active site and hopefully gain insight into what substates it may act upon. Successful elucidation of CmlS'activity may lead to furthering antibiotic research and hopefully produce new drug candidates.